1. Field
This invention relates to trampoline recreational equipment. Specifically, this invention is directed to a resilient trampoline suspension system for use in connecting an essentially stretchless jumping platform to a rigid support frame.
2. State of the Art
Trampolines of various configurations are well-known in the art. A typical construction includes a sheet of fabric which is generally quadrilateral or circular in shape. The sheet defines a jumping surface and is tensionally suspended in a substantially horizontal plane from an essentially rigid or sometimes resilient frame structure. The fabric sheet is traditionally connected to the frame by means of an elastic suspension or connection system; e.g., coil springs connected to the sheet along its edge. The springs are used to tension the sheet essentially taut while also imparting an elastic quality to the sheet/spring assembly.
Many traditional means of connecting the springs to the sheet of fabric have proven less than satisfactory in achieving a connection which is both easily manufactured and durable over an extended use period. For example, in one known connection arrangement, the edge of the sheet of fabric is turned under to form a hem which is stitched by a conventional sewing operation. The hemmed edge is utilized as a mounting platform for a securement ring, which ring is adapted in turn for connection to a coil spring. Typically, the ring is connected to the hemmed edge by an elongated fabric strip which passes through the ring. The proximal and distal ends of the strip are thereafter sewn to the hemmed edge, securing the ring to the fabric sheet. Generally, a further strengthening of the mounting platform is accomplished by adding a reinforcing piece of fabric proximate the hemmed edge of the fabric sheet. The sewing thread, in connecting the various fabric members, passes through the doubled layer of the sheet of fabric, the ring-retaining fabric strip, and then the reinforcement fabric. Noticeably, the manufacture and installation of this mounting means is time-consuming in terms of manufacturing requirements.
In an alternate arrangement, the fabric sheet is connected to the springs via metal eyelets which are positioned in the fabric sheet along its perimeter. The eyelets individually define an aperture adapted to receive and retain a hook-like structure affixed to the coil springs.
A trampoline constructed under either of these methods presents disadvantages in use. First, trampolines placed outdoors are subjected to ultraviolet radiation from exposure to the sun. The ultraviolet rays induce a deterioration of the strong synthetic threads presently used in constructing trampolines. Under typical outdoor use conditions, a spring/fabric connection constructed as first described above is believed to have a useful life of approximately two years. Even in those applications where special ultraviolet-resistant thread is used, the thread may deteriorate, though at a somewhat slower rate.
Another disadvantage in the described methods is the limited capability of conventional connection arrangements to distribute the forces transferred by the coil springs to the fabric sheet. In typical use, the conventional connection arrangement transfers the force to substantially small areas along the edge of the sheet of fabric. In the case of the ring and fabric strip arrangement, the force is transmitted at the junction of the ends of that strip and the fabric sheet. In the eyelet arrangement, the force is applied about the circumference of the eyelet. This concentrated force application often exceeds the tensile strength of the fabric in those small areas and may therefore result in distortion or unravelling of the weave of the fabric sheet in extended use.
Given the danger which may result from a deteriorating connection structure, the user is impelled by safety considerations to periodically inspect and repair where necessary and in some cases replace the entire sheet of fabric. Recognizably, this replacement results in a considerable cost for the user.